ABSTRACTMyoepitheliomas of the extremity are rare and usually benign, while a minority display malignant features. This case demonstrates the diagnosis and management of myoepithelioma within the carpal tunnel. Clinical and radiological tumour features were evaluated. Hematoxylin and eosin stained tumour sections were examined, and immunohistochemistry was performed. Histology revealed a nodular mass of epithelioid cells in clusters within a myxoid/chondroid stroma. No mitoses were noted. Cytokeratins, neuron-specific enolase, synaptophysin, glial fibrillary acidic protein, and S100 were positive on immunohistochemistry. A literature review revealed very few prior reports of myoepithelioma in the wrist, and limited data concerning any relationship between recurrence and quality of surgical margins. In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features. Surgical margins noted in future case reports will aid clinical decision making.

Mentions:
A second MRI scan (Fig. 2), performed 12 months later, showed the tumour size had not changed from the previous scan and the long axis of the mass remained parallel to that of the profundus tendon. Fluid signal was noted predominantly but with the addition of irregular T2 hypointense septations within it, which enhanced with contrast. The mass was also found to displace flexor digitorum superficialis (FDS) tendons to the ring and little fingers in a volo-ulnar direction and the FDS tendons to the index and middle finger in a volo-radial direction (Fig. 2c, d). The median nerve was compressed anteriorly between the FDS tendon slips to the middle and index fingers and the overlying flexor retinaculum (Fig. 2c, d). Associated T2 hyperintensity of the median nerve was demonstrated over its passage through the carpal tunnel.

Mentions:
A second MRI scan (Fig. 2), performed 12 months later, showed the tumour size had not changed from the previous scan and the long axis of the mass remained parallel to that of the profundus tendon. Fluid signal was noted predominantly but with the addition of irregular T2 hypointense septations within it, which enhanced with contrast. The mass was also found to displace flexor digitorum superficialis (FDS) tendons to the ring and little fingers in a volo-ulnar direction and the FDS tendons to the index and middle finger in a volo-radial direction (Fig. 2c, d). The median nerve was compressed anteriorly between the FDS tendon slips to the middle and index fingers and the overlying flexor retinaculum (Fig. 2c, d). Associated T2 hyperintensity of the median nerve was demonstrated over its passage through the carpal tunnel.

Bottom Line:
No mitoses were noted.In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features.Surgical margins noted in future case reports will aid clinical decision making.

ABSTRACTMyoepitheliomas of the extremity are rare and usually benign, while a minority display malignant features. This case demonstrates the diagnosis and management of myoepithelioma within the carpal tunnel. Clinical and radiological tumour features were evaluated. Hematoxylin and eosin stained tumour sections were examined, and immunohistochemistry was performed. Histology revealed a nodular mass of epithelioid cells in clusters within a myxoid/chondroid stroma. No mitoses were noted. Cytokeratins, neuron-specific enolase, synaptophysin, glial fibrillary acidic protein, and S100 were positive on immunohistochemistry. A literature review revealed very few prior reports of myoepithelioma in the wrist, and limited data concerning any relationship between recurrence and quality of surgical margins. In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features. Surgical margins noted in future case reports will aid clinical decision making.